An image forming apparatus such as a multi function peripheral (MFP) that forms an image on a recording medium, for example, a sheet is proposed. The image forming apparatus includes a development unit that develops an electrostatic latent image formed on a photoreceptor using a two-component developer formed of, for example, a toner and a carrier, as a color material. The development unit stirs the two-component developer to charge the toner. The development unit supplies the charged toner to the photoreceptor to develop the electrostatic latent image of the photoreceptor, thereby forming a toner image. The image forming apparatus transfers the toner image onto the sheet and further fixes the toner image, thereby forming an image on the sheet. Since the toner is consumed for each image forming process, a new toner is supplied to the development unit when an internal toner concentration is a predetermined value or less.
A remaining toner which is not used for each image forming process is accumulated in the development unit. The accumulated toner is stirred whenever an image is formed, and charging performance thereof gradually deteriorates. The deteriorated, toner causes deterioration of the formed image, such as attachment to a non-image area of the sheet. In the image forming apparatus, for example, when the image forming process of a low printing rate with low toner consumption is continued, the deteriorated toner is easily accumulated in the development unit, and a trouble such as deterioration of the formed image easily occurs.
Accordingly, in order to solve the problem of the deteriorated toner, the image forming apparatus periodically performs a toner refresh process between the image forming processes. The toner refresh process is a process of forcibly forming an image on a photoreceptor by the development unit to consume the deteriorated toner in the development unit.
In addition, an image forming apparatus which can perform an image forming process of forming an image on a sheet using a color-erasable toner, and an erasing process of erasing the image formed on the sheet using an erasable toner has been developed. Even in the image forming apparatus, in order to solve the accumulation of the deteriorated toner, it is conceivable to periodically Perform the refresh process between the image forming processes. However, during the period of performing the refresh process, another process cannot be performed, and thus it is preferable that the period of performing the refresh process be short as possible.